=Paper=
{{Paper
|id=Vol-2180/paper-13
|storemode=property
|title=The SPARQLING System for SPARQL Queries over GRAPHOL ontologies
|pdfUrl=https://ceur-ws.org/Vol-2180/paper-13.pdf
|volume=Vol-2180
|authors=Sara Di Bartolomeo,Gianluca Pepe,Valerio Santarelli,Domenico Fabio Savo
|dblpUrl=https://dblp.org/rec/conf/semweb/BartolomeoPSS18a
}}
==The SPARQLING System for SPARQL Queries over GRAPHOL ontologies==
https://ceur-ws.org/Vol-2180/paper-13.pdf
The S PARQLING system for SPARQL queries over
G RAPHOL ontologies
Sara Di Bartolomeob , Gianluca Pepeb ,
Valerio Santarellia,b , Domenico Fabio Savoa,b
(a) Sapienza Università di Roma
hlastnamei@diag.uniroma1.it
(b) OBDA Systems
hlastnamei@obdasystems.com
Abstract. In this demo we present the S PARQLING system for SPARQL query
building based on the G RAPHOL visual language for ontologies. The characteriz-
ing feature of S PARQLING is the idea to preserve and take advantage of the native
diagrammatic representation of G RAPHOL ontologies, allowing the user to navi-
gate it, and to construct a graph-based representation of the query over it through
a simple point-and-click mechanism. The system then automatically transforms
the graphical query into the SPARQL syntax.
1 Introduction
In computer science, an ontology is the formal conceptualization of a domain of interest,
and its purpose it to favor sharing and integration of knowledge among information
systems and to provide an abstract representation of the domain which is understood
and agreed upon by ontology designers and domain experts.
Ontologies commonly are formalized through languages such as Description Log-
ics [4] (DLs) or the W3C standards RDF(S)1 and OWL 22 . Typically however, it is
rare to encounter people in industrial settings who possess the skills to interpret the
logic-based formulas used in such languages. This represents a significant issue in the
adoption of ontologies in these settings, because it creates a bottleneck in the ontol-
ogy design phase, where ontology engineers must work with domain experts. To mit-
igate this problem, numerous graphical languages for ontologies [5, 7, 10] have been
proposed in recent years, and among the latest of these efforts is G RAPHOL [6, 11].
The main features of G RAPHOL are that it presents an entirely graphical syntax based
on Entity-Relationship diagrams, it has a formal DL-based semantics, and is able to
fully capture OWL 2. The effectiveness of G RAPHOL as the language for representing
ontologies has been validated in several recent and ongoing research and instrustrial
projects [2, 3].
Ontologies, aside from acting as a conceptualization of a domain, are gaining steam
as a means to access and manage data. In fact, triple stores are now commonly used to
1
http://www.w3.org/TR/rdf-primer-20040210/
2
http://www.w3.org/TR/owl2-primer
Fig. 1. The user interface of the S PARQLING system.
manage (Linked) enterprise data [15], and semantic technologies such as ontologies are
used to manage legacy data stores [12]. In these settings, the standard query language
for triple stores and ontologies is SPARQL3 . SPARQL, while simpler in structure than
traditional query languages such as SQL, still suffers from the same drawback as tradi-
tional ontology languages, i.e., it is not easily understood by people who lack specific
training or background. Going back to the idea of using graphical solutions to support
usability, there have been several proposals for visual SPARQL query building systems
in recent years, from those that allow query formulation in natural language or through
context-sensitive completion mechanisms [9, 13], to those that provide support for con-
structing graph-based representations of the SPARQL query [1, 8, 14].
In this demonstration, we present the latest of these systems, S PARQLING. S PAR -
QLING is a web application that allows to build SPARQL queries based on the
G RAPHOL language, whose characterizing feature is the idea to preserve and take
advantage of the native diagrammatic representation in G RAPHOL of the ontology.
Through S PARQLING’s interface, the user can navigate the ontology and formulate a
graph-based representation of a SPARQL query over it through a simple point-and-click
mechanism. To illustrate the main features of S PARQLING, we will invite attendees of
the demo to experiment it on the Base Register of Individuals, Families, and Cohabita-
tion (BRIFC) ontology, developed during a joint project between Sapienza University
of Rome, OBDA Systems, and the Italian National Institute of Statistics (Istat) [3].
S PARQLING is an open-source project, available on Github4 , and is supported by
OBDA Systems5 .
3
https://www.w3.org/TR/rdf-sparql-query/
4
https://github.com/picorana/painless_sparql
5
https://www.obdasystems.com/
2 The S PARQLING System
S PARQLING is a web-based application for constructing SPARQL queries by exploiting
the G RAPHOL representation of the ontology. The development of S PARQLING origi-
nates in systems for Ontology-based Data Management [12], hence it currently supports
the conjunctive query fragment of SPARQL. As shown in Figure 1, the system interface
is divided in three main sections, which we describe briefly.
The main area contains the G RAPHOL diagrams. Through the tools in this area,
the user can navigate and inspect the ontology along with its documentation. The
G RAPHOL representation allows the user to clearly perceive its structure and content,
facilitating the task of constructing the query over the ontology. Indeed, the mental pro-
cess of writing a query is natural when looking at a G RAPHOL diagram because it recalls
the act of tracing a path on it. Through the interaction with the G RAPHOL diagram the
user builds the ontology query, whose visual representation, called query graph is pro-
vided in the second area. This representation has the structure of a graph, to naturally
recall SPARQL’s basic graph patterns, where nodes represent subjects or objects of each
triple pattern, and edges represent predicates. To provide a visual correspondence with
G RAPHOL, the graphical representation of the ontology predicates in the query graph
is the same as in G RAPHOL. The third section shows the SPARQL representation of
the query, which the user can inspect or modify. Each change in the SPARQL query is
immediately mirrored in the query graph, and viceversa, to keep the two versions con-
stantly aligned. The user can choose to interact with both representations of the query,
or only with one of the two, according to his preference.
To add a triple to the basic graph pattern of the query, the user double clicks on a
predicate symbol in the G RAPHOL diagram. According to the specific predicate symbol,
the corresponding edge and nodes are automatically added to the query graph. Actions
on specific nodes of the graph are performed through contextual menus that appear by
right clicking on a node.
The application is developed in JavaScript, using the Cytoscape.js library6 for the
rendering of the G RAPHOL diagram and the query graph, and the cola.js library7 for the
force-directed layout of the query graph.
3 Application scenario and Demo Section Overview
We demonstrate the S PARQLING system through the Base Register of Individuals, Fam-
ilies, and Cohabitation (BRIFC) ontology, developed in Graphol during a joint project
between Sapienza University of Rome, OBDA Systems, and the Italian National Insti-
tute of Statistics (Istat) [3].
The BRIFC ontology depicts a portion of the domain of the Italian Integrated Sys-
tem of Statistical Registers of Istat, which acts as the base for Istats production surveys.
The ontology is composed of two modules: the first regarding people, their family re-
lationships, and their level of education; the second regarding the Italian territory and
citizen residential data. In the project, the ontology was developed in support of the
6
http://js.cytoscape.org/
7
http://ialab.it.monash.edu/webcola/
adoption of the OBDM approach for data access and quality checking. The experi-
mentation has confirmed the effectiveness of this approach for these purposes, and of
G RAPHOL as a means of representation of the ontology both in the design phase and
in the deployment phase. Currently, we have given way to the experimentation of the
S PARQLING system as the tool for the production of SPARQL queries in the project.
During the demo, attendees will interact with the S PARQLING system, inspecting
the G RAPHOL BRFIC ontology and experiencing how the SPARQL query construction
process is simplified through the use of the system interface. We will also show how
S PARQLING can interact with the SPARQL endpoint in the Mastro system8 for OBDM.
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8
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